Sam Querrey and John Isner will join Davis Cup regulars Bob and Mike Bryan for the U.S's first-round tie against Serbia in March.
With Andy Roddick and James Blake both opting to skip the tie, Querrey and Isner will be the team's two singles players. Isner will be making his Davis Cup debut, while Querrey will be trying to score his first win after going 0-2 against Spain in 2008.
"This is something I've been looking forward to ever since I started playing pro tennis," said Isner.